When a vertical blower is used as an induced draft fan, normally it is installed in a base section of a smokestack. This is done because this blocks the noise caused by the blower, and shelters the blower from wind and rain, thus avoiding the necessity for a separate shed for accommodating the blower, and the like.
FIGS. 1-3 show a common arrangement of this type of vertical blower, in which reference numeral 1 designates a smokestack installed on a foundation E, and at the base section of the smokestack 1 are provided a lowermost floor 1a consisting of the foundation E and upper floors 1b, 1c and 1d projecting inwardly from the inner circumferential wall of the smokestack 1 at appropriate intervals above said floor 1a in a multi-layer form. Among these floors, on the floor 1b, or the so-called second floor, are installed, in the illustrated embodiment, two motors 2. In addition, an opening h.sub.2 is provided in said floor 1b through which a blower 3 to be described later can be passed. Two blowers 3 are detachably mounted on the third floor 1c so that they can be driven respectively by said two motors 2, and they are adapted to suck exhaust gas through flues D connected to an exhaust smoke source (not shown) and to blow the gas through ducts d connected to the blowers via expansion joints 4. It is to be noted that the top level floor 1d has the role of supporting the ducts d and is also useful for performing maintenance operations for associated instruments within said ducts d.
When maintenance, inspection and repair operations for the vertical blower 3 that is disposed at the base section of the smokestack in the above-described manner are required, as shown in FIGS. 2 and 3 the blower 3 is disconnected from the expansion joint 4 and is moved laterally, sliding along rails 5 that are preliminarily laid on the floor 1c as best seen in FIG. 2, subsequently lifted by a weight-lifting apparatus such as a hoist that is fixedly mounted on the lower surface of the floor 1d, and then it is lowered down to the lowermost floor 1a through the openings h.sub.2 and h.sub.3 provided in the floor 1c and in the floor 1b, respectively. When the blower is on said floor 1a, the rotor chamber is opened to perform the maintenance, inspection and repair operations.
The disadvantages of this arrangement are that a rather large space is required on the floor 1a, resulting in an increase in the construction cost of the smokestack, and, in order to lower the blower 3 onto the floor 1a, a lot of labor is required and the lowering operation involves some danger.